Depression by estrogen of electrical activity in the hypothalamic ventromedial nucleus of female cats

Abstract

(1) Hypothalamic and cortical EEG activities were telemetered from freely-moving ovariectomized female cats during mating tests with a vigorous male conducted over periods of many weeks. (2) Records were analyzed for long-term energy changes in 3 frequency bands: 4–8, 8–16 and 16–32 Hz. In Hvm, energy levels (Voltage Indices) were higher in the higher frequency bands while the reverse trend was observed in anterior and posterior hypothalamus. (3) Estrogen treatment had widespread effects on energy levels in the brain, but consistently depressed energy levels in Hvm, particularly in the highest frequency band. (4) Estrogen treatment did not consistently exert this effect in anterior and posterior hypothalamus or in cortical sites. (5) Behavioral factors also contributed to the effects observed. Although these were difficult to interpret, the particular depression observed in Hvm during mating activity did not occur elsewhere. (6) There is evidence that these localized changes in EEG activity relate to the regulation of estrous behavior.